An array substrate of a Thin Film Transistor (TFT) Liquid Crystal Display (LCD) (TFT-LCD) is driven in a matrix of rows and columns, where the matrix of rows and columns is formed by N rows of gate lines and M columns of data lines which intersect each other to drive respective pixel elements in the matrix of rows and columns.
A common electrode line Vcom in the TFT-LCD traverses the entire display area. FIG. 1 illustrates a schematic structural diagram of an equivalent circuit driving pixel elements in a conventional TFT-LCD, where respective TFTs have gates connected with corresponding gate lines, sources connected with corresponding data lines and drains connected with pixel electrodes in corresponding pixel elements, and the respective pixel elements and the common electrode line Vcom (the common electrode line Vcom is typically at a negative level) constitute equivalent capacitors Ce. Particularly, the TFTs in FIG. 1 are n-type TFTs. Alternatively, the TFTs in the pixel circuits of the TFT-LCD can be p-type TFTs, or some TFTs in the pixel circuits of the TFT-LCD are p-type TFTs, and other TFTs are n-type TFTs.
The respective gate lines in the TFT-LCD are driven sequentially by a gate drive circuit in the TFT-LCD, and a data line is powered by a gamma circuit in the TFT-LCD at the voltage corresponding to an image to be displayed by pixels connected with the data line, that is, the respective pixel electrodes electrically connected with the data line are provided with data voltages so that the image to be displayed can be displayed at the respective pixels. Half the sum of a positive voltage at a grayscale of a pixel in a display panel at the edge of the display area and a negative voltage at the grayscale, i.e., the voltage Vcom of the common electrode line required for the pixel in the display panel at the edge of the display area, is not equal to half the sum of a positive voltage at a grayscale of a pixel in the display panel at the center of the display area and a negative voltage at the grayscale, i.e., the voltage Vcom of the common electrode line required for the pixel in the display panel at the center of the display area due to some reason in a process of manufacturing the display panel, and the same voltage is provided on the common electrode line throughout the display panel, so the flicker at the pixel in the display panel at the edge of the display area may differ from the flicker at the pixel in the display panel at the center of the display area at the same common voltage Vcom, thus resulting in non-uniformity of flicker over the display panel.
For example, given an existing display panel, the reliability of which was tested at high temperature and high humidity, the flicker at a pixel at the center of a display area of the display panel (the flicker at a pixel can be measured directly by an instrument, and the larger a measurement value is, the higher the flicker at the pixel will be) was −51.01 dB, while the flicker at a pixel at the edge of the display area of the display panel was −20.24 dB, at the voltage of −0.45V on a common electrode line Vcom, and at this time the flicker at the pixel at the edge of the display area of the display panel was higher than the flicker at the pixel at the center of the display area of the display panel; and the flicker at the pixel at the edge of the display area of the display panel was down to only −50.97 dB, while the flicker at the pixel at the center of the display area of the display panel was −18.65 dB, at the adjusted voltage Vcom of −0.3V on the common electrode line, and at this time the flicker at the pixel at the center of the display area of the display panel was higher than the flicker at the pixel at the edge of the display area of the display panel. Given the same voltage Vcom of the common electrode line throughout the display panel, the flicker on the display panel may appear non-uniform at the same voltage Vcom of the common electrode line throughout the display panel.
In summary, different common voltages Vcom are required for the different pixels in the conventional display panel for obtaining the uniformity of flicker (that is, the lowest flicker throughout the display area of the display panel), that is, the voltage Vcom of the common electrode line required for a pixel at the edge of the display area of the display panel is different from the voltage Vcom of the common electrode line required for a pixel at the center of the display area. The same voltage Vcom of the common electrode line throughout the same display panel may result in the uniformity of flicker throughout the same display panel.